The present invention relates to a process for preparing a liquid aroma containing concentrated coffee aromatic compounds from a grinder gas frost. The liquid aroma produced according to the invention may be used to aromatize a coffee substrate, such as a spray dried, freeze dried or roasted and ground coffee, or a glyceride, such as a coffee oil, or some other food material.
Soluble beverage powders such as spray dried coffee are relatively devoid of aroma as compared to their source or parent material, namely, roasted and ground coffee. Low aroma intensity also exists in certain types of roasted and ground coffee material such as most decaffeinated coffees and the compressed roasted coffee materials described in U.S. Pat. Nos. 1,903,362 to McKinnis, 3,615,667 to Joffee and 4,261,466 to Mahlmann et al. These low-aroma beverage powders and products have an initially low quantity of aroma, such that upon the initial opening of the container containing the product by the consumer, only low aroma impact is detected, and whatever amount of aroma is present in the product is rapidly given up after initial opening of the container, such that subsequent openings of the container during a typical in-use cycle for the product evolve little or no aroma.
To date most efforts to add natural aroma to soluble coffee products have focused on the addition of roasted coffee aroma to soluble coffees such as spray or freeze-dried coffee. The vast majority of commercial soluble coffees are combined with coffee oil such as by spraying the soluble coffee prior to packaging with either a pure or an aroma-enriched coffee oil. In this manner the soluble coffee material will have an aroma more akin to non-decaffeinated roasted and ground coffee. The addition of oil is usually effected by the well-known oil plating technique (shown in U.S. Pat. No. 3,077,405 to Clinton et al. and U.S. Pat. No. 3,148,070 to Mishkin et al.) or by oil injection (shown in U.S. Pat. No. 3,769,032 to Lubsen et al.).
Coffee oil with or without added aromas has been the preferred medium employed to aromatize coffee material since such products may still be designated as being pure coffee; however, techniques developed for the production of coffee oil such as solvent-extracting or expelling coffee oil from roasted coffee are not particularly desirable since the manufacturer is left with either solvent-containing roasted coffee or expelled cake, both of which must be either further processed or discarded. The prior art has certain other drawbacks including the poor flowability of plated coffee particles and the undesirable droplets of oil that can appear on the surface of a liquid beverage prepared from the plated coffee. To overcome the disadvantages and drawbacks of that use of coffee oil or other glyceride material, it is desired that an alternative medium be developed for aromatizing a coffee material.
Johnston and Patel et al. in U.S. Pat. Nos. 2,306,061 and 3,823,241 respectively, teach the aromatization of a beverage substance with coffee grinder gas by directly contacting grinder gas with a beverage substance which has been chilled to a temperature of at least -15.degree. C. These references eliminate the use of coffee oil as an aromatization medium by enabling direct contact of grinder gas with the substrate to be aromatized. However, these methods are not commercially advantageous for several reasons, the primary reasons being that direct contact of grinder gas with a substrate is an inefficient means of mass transfer, that the hold-up time required for said contact is inefficient in a continuous coffee process, and that control of aromatization levels is impossible according to the cited methods.
The coffee art is replete with methods for aromatizing a glyceride with a grinder gas frost, said grinder has frost having been condensed by contact with a chilled medium. For example, U.S. Pat. No. 4,119,736 to Howland et al. discloses removal of a water phase from a pressure vessel containing condensed grinder gas at a pressure of in excess of 506.2 psia and a temperature of greater than 32.degree. F., contacting the demoisturized grinder gas with a glyceride, and slowly venting the pressure vessel. Mahlmann in U.S. Pat. No. 3,979,528 discloses a method for aromatizing a glyceride by contacting it with a grinder gas frost in a pressure vessel at various conditions. Among the conditions disclosed by Mahlmann is a rapid pressure release of the pressure vessel to atmospheric pressure at a temperature below room temperature. However, in these references, as is true throughout the coffee art, substantial coffee aromas are lost to the atmosphere by venting rather than being fixed on a food substrate during an aromatization step.
Thus, it is an object of the present invention that an efficient means for aromatizing a substrate be found.
It is a further object that the aromatized substrate possess a coffee aroma comparable in quality to freshly ground roasted coffee.
It is another object that the yield of aromatized substrate per volume of coffee grinder gas be increased over prior art systems.